The increasingly widespread use of fine-pitch Ball-Grid Array (BGA), Chip Scale Packaging (CSP), and other evolving technology form-factors means that new fabrication techniques must be used to create printed circuit boards (PCBs) and architectures for placing components thereon. Additionally, efforts to reduce costs further compound the problems associated with the smaller, denser, lighter, and faster systems that are evolving.
As integration continues to shrink the space required for mounting the active components in an electronic device, the routing density and the mounting density of the accompanying passive components becomes an increasingly problematic issue. Capacitors and resistors in chip component format can actually take up more space than the active circuit components, and cause great difficulty in circuit design. Many of these passive components are used as noise protection and grounding shunts on integrated circuit inputs and outputs. Ideally they should be located as close as possible to the actual IC pin connection. Since many IC's now come packaged in ball grid array format, it is impossible to locate a chip component directly adjacent to the lead it is supposed to connect.
One solution put forward is to integrate the passive components into the silicon on an integrated circuit. Since integration into the silicon is not often very practical, designers have sought to integrate the passives into the substrate. The most cost effective substrate is usually an organic printed circuit board. Integrating capacitors into these types of structures presents an obvious problem of size. The available space and layering only permits a small number of very low value capacitors to be integrated using the standard organic layer structure.
There are a couple of avenues being pursued for integrating resistors. The resistive foil layer (Ohmega-ply) and vacuum deposited resistor methods each present barriers of cost and infrastructure. Polymer thick film resistors are notoriously unreliable and variable, presenting a problem with achieving tight tolerances.
Thus, a reliable method and assembly for integrating components on a circuit board such as a multi-layer board that overcomes at least some of the detriments described above would be desirable.